Xerographic processes were first used in the 1930s by Chester Carlson to reproduce images. In the 1960s, Xerox Corporation produced the first commercial photocopier based on Xerographic principles, the Xerox-914. In the 1970s, Xerox Palo Alto Research Center (PARC) used many of the same principles to develop the laser printer.
Normal Xerographic laser printing creates a charge pattern on a photoreceptor. To create the charge pattern, a corotron charges all of the pixels on a photoreceptor. A scanned laser beam or laser beams discharge selected photoreceptor pixels. After completion, a charge distribution representing an image remains on the photoreceptor.
The photoreceptor charge distribution is exposed to toner particles. Charged photoreceptor pixels attract toner particles. The resulting photoreceptor toner distribution substantially matches the charge distribution. A paper brought into contact with the photoreceptor receives the toner from the photoreceptor. Heat and fuser fixes the toner in position on the paper.
One problem with the Xerographic laser printing system is that the laser scanning system is delicate and expensive. The optics used to precision scan and direct the laser beam to each pixel represents a significant barrier to allowing laser printers to compete with ink jet printers on price.
Thus a more inexpensive method of charging and discharging a photoreceptor is needed.